Underground and submersible junction bus connectors are widely used in utility distribution systems. Typical of such connectors are the connectors sold under the trademark ESP.RTM. by Eritech, Inc. of Aberdeen, N.C. under the model designations UC, HFS, RD, UCD, BRD, and UCB. Such connectors are commonly characterized by a rigid bar or bus from which projects a plurality of relatively closely spaced circular posts. The thickness of the bar or bus may typically be about one tenth or less the projection of the posts. The number of posts may vary from as few as two to as many as eight or more. Such submersible connectors are widely used in connections to transformers underground in electrical power distribution systems.
There are generally two types of such connectors. One employs hollow posts for each terminal or outlet and one or more set screws to clamp and secure the end of a conductor within each hollow post. Another type utilizes a flat pad on the end of an otherwise solid post. One or more compression fasteners secure a conductor lug to the flat pad. The flat pad may extend for approximately the outer two thirds of the post, and the outer end of the pad surface may include an alignment recess interfitting with the conductor lug to maintain lug and post alignment. With such connectors, high amperage connections can quickly be made.
Because of the complex configuration of the connectors which include a lot of non-parallel surfaces, they are typically made by fabrication with weldments or from aluminum alloy castings, all at considerable cost. One of the principal cost problems in casting is that separate molds or dies are required for each model of connector, and within the model for each number of terminals or outlets. Accordingly, the investment in molds and core molds, or dies alone is staggering.
Moreover, the castings have to be made in a job shop foundry or die casting shop which further raises the cost. While some large scale foundries or die casting shops can afford the environmental strictures now required, many smaller foundries or shops can not, and many have closed, requiring importation of castings and/or much higher costs. In addition to higher costs, uncertainty of supply is a problem with casting.
In addition to the economic and environmental problems, castings present some technical problems as well. The surface texture is rather rough which is not ideal for higher amperage electrical connections. They require a considerable amount of grinding or surface finishing after casting and this is usually a manual labor intensive operation. They still require tapping of holes for clamping or set screws, and the casting makes alignment and jigging problems more complex. Also, the physical properties and microstructure of castings can be less than desirable. For example, an extruded and machined part will have considerably higher mechanical strength, better conductivity, better appearance, and improved surface contact with the conductor.
The extrusion process, particularly hot extrusion, has been widely used to produce a variety of parallel surface shapes including some electrical connectors. Such connectors have relatively simple square, rectangular or other parallel face surface shapes, and secondary machining operations are generally limited to drilling and tapping in such parallel face surfaces. Examples of such extruded connectors are those sold under the trademark ESP.RTM. by Eritech, Inc. of Aberdeen, N.C., under the model designations UP, UPSO, UPM, UPT and UPL. Using the extrusion process to produce such relatively simply parts results in quality connections which are economical to produce.
It would, accordingly, be desirable to be able to produce the more complex connectors having a lot of non-parallel surfaces by an extrusion-machining process to produce both improved and lower cost connectors.